Biologists use chromatin immunoprecipitation (or ChIP) to determine the binding sites of DNA-binding proteins. In the example presented in the image, they use an antibody against histone proteins to determine the position of all of the histones on the DNA, but by using different antibodies, you can determine the positions of different proteins. For example, if you are interested in a certain transcription factor, you can generate an antibody against the transcription factor, perform the ChIP experiment with that antibody, and sequence the resulting DNA to find out where in the genome your transcription factor binds. This sequence information is extremely useful. For example, comparing the DNA binding sequences can give you an idea of the types of sequences the transcription factor likes to bind and looking at the regions surrounding the sequences you obtain from the ChIP experiment can give you an idea of the types of genes that the transcription factor regulates and other DNA-binding proteins that your transcription factor may cooperate with.